1. Field of the Invention
The present invention relates generally to a baffle assembly used to seal or baffle a hollow body through the use of a heat activated expandable material.
2. Background Art
Hollow bodies or cavities, such as pillars forming part of the chassis of an automobile, are good transmitters of sound due to their hollow configuration. In operation of an automobile, for instance, the sound generated by the tires, the engine, and/or the transmission can be readily transmitted through the hollow portions of the vehicle, such as A, B and C pillars, and can be audible from within the passenger compartment of the vehicle. This transmission of sound is usually undesirable. To address this problem, manufacturers have placed baffle assemblies within the hollow portions of the vehicle to seal them off. In this way, rather than having a network of tunnels for the transmission of sound throughout the entire chassis of a vehicle, there are a series of sealed compartments which are better able to isolate the sound and reduce its transmission into the passenger compartment.
One way of baffling and/or sealing a hollow compartment, such as an A, B or C pillar of an automobile, is to place a thermally expandable material (sometimes referred to as a “mastic,” it being understood that such materials may be either tacky or non-tacky at room temperature) within the hollow compartment and then activate the material by elevating the temperature of the expandable material to its activation temperature. Once activated, the material expands, essentially filling an entire cross-sectional segment of the hollow compartment, thus sealing it.
In a typical application, the mastic is attached to a substrate. The substrate holds the mastic in position within the hollow compartment prior to and during thermal expansion. A mounting member such as a bracket or other fixture connects the substrate to an interior wall of the compartment. In other applications, the mounting member may be separately fabricated and then attached to the substrate.
For cost effectiveness, it is desirable to use mastics having greater expandability because this reduces the amount of mastic material required to seal and/or baffle a hollow compartment. It is also desirable to extrude the mastic material rather than injection mold it because of lower related tooling costs.
Another problem baffle assembly manufacturers face is the need to accommodate differently configured hollow compartments having differently dimensioned cross-sections. It is desirable to have a substrate that can fit in compartments having both large and small cross-sectional dimensions. While the mastic generally expands to fill the compartment that it is mounted in, the substrate, which has a melting point higher then the activation temperature of the mastic, generally remains dimensionally constant. Thus, in instances where the compartment is cross-sectionally smaller than an outer perimeter of the substrate, the substrate generally cannot be used since the substrate will not fit within the component.
Additionally, in some applications, such as automotive applications, the thermal activation of the mastic occurs during a baking process wherein an e-coat or other protective coatings are cured. In such applications, it is necessary that there be clearance between an edge of the substrate and the internal wall of the compartment that is to be sealed and/or baffled. This clearance allows the e-coat to flow past the substrate when the compartment is submerged in the e-coating material. It is therefore desirable to have a substrate that can be used with compartments having both large and small cross-sectional dimensions and that does not obstruct the flow of e-coat materials. The present invention addresses these and other problems.